FR2632865A1 - HIGH PERFORMANCE DEFIBRILLATOR WITH SEVERAL ELECTRODES OUTSIDE THE HEART - Google Patents

Abstract

High performance defibrillator. Defibrillator characterized in that it comprises at least one discharge electrode 10 located in the right ventricle and several electrodes external to the heart, 16 to 20 remote from the latter in different directions. This invention is of interest to manufacturers of implantable defibrillators.

Description

The present invention relates to a

  high-performance

  inner trode and several external electrodes in the heart. Various abnormalities of heart function result in an irregular beat and, in extreme cases, cessation of blood pumping by

  ventricular fibrillation leading to death.

  The purpose of a defibrillator is to provide sufficient current from a fast discharge of a capacitor, by means of a suitable electric shock, to simultaneously excite and depolarize the cells of the largest possible mass of the ventricular myocardium. fibrillation and leading to the resumption of rhythmic contractions of normal functioning of the heart. At a lower degree of severity, this kind of disorder is called ventricular tachycardia. This disorder can also be treated by an electric shock. The treatment is then called cardioversion and the device

  possessing this cardiovertor function.

  In what follows, the terms defibrillation and defibrillator cover the function of

  cardioversion and the device that implements it.

  An automatic defibrillator

  this electrical shock immediately upon detection of a rhythm disorder or a stoppage as indicated above. The search for miniaturization is a constant concern in the design of devices implanted in the human body. This requirement plays even more in the context of a complex and automatic system such as

an automatic defibrillator.

  Indeed, the defibrillation function and,

  correlatively, the cardioversion function requires

  at least two electrodes between which

  the discharge, and preferably at least one additional electrode for the detection of disturbance of the rhythm and control of the discharge. It requires

  also the appropriate circuits relating thereto.

  Moreover, the management of automatic operation implies the existence of adapted circuits which

  add to the size of the unique case

  all the circuits of supply, supervision and

lance and command.

  In addition, the capacitor, because of its

  capacity, occupies a relatively important place

  aunt. Can not miniaturize anymore the circuits and

  the battery in the current state of technology, the ef-

  strong must refer to the capacitor.

  Major technological progress and put in

  point made by the applicant have, by means of new

  materials, suitable winding and know-how

  extended, significantly reduce the size of conden-

with equal capacity.

  One of the possibilities of diminishing capacity

  capacitor and therefore its size would be the increase

  tation of its charging voltage. However, the character of

  observed on the human body of the poten-

  resulting currents and currents, does not allow for

consider this solution.

  Another objective, which has appeared recently with regard to automatic implantable defibrillators, is to aim for a mode of implantation that does not require thoracotomy. The present invention sets itself as a goal

  to simultaneously fulfill both of the above requirements.

  which appear contradictory for the following reason. The implantation methods known to date do not

  requiring no thoracotomy inevitably leads to

  loss of energy that needs to be offset by

  better performance of the already technolo-

  limited in weight and size.

  These best performances are represented

  through improvements in weight and weight gain.

  and an appropriate configuration or general structure to significantly reduce energy

  effective defibrillation and hence cardioversion.

  In the feeling of having arrived at one. limit

  the applicant's researchers turned their attention to

  towards the possibilities of reducing the energy threshold of the discharge corresponding to a given efficiency rate. It is known that at a given efficiency rate, the discharge must exceed a minimum energy threshold for

cause defibrillation.

  If the value of this threshold depends on the characteristics

  the physical parameters of the person, it also depends on other parameters and, to a large extent, a limited number of factors highlighted, significantly and directly affecting the effectiveness of the electrode system in obtaining a better result

defibrillation statistics.

  These are the two important factors

  the energy efficiency of defibrillation characterized by the ratio between the energy applied to the myocardium and the total energy delivered by. the capacitor; The homogeneity of the current density across the myocardium. These two factors themselves depend on many parameters and are directly related to the size of the proportional capacitor itself to the energy

that he can store.

  In this spirit, and in the light of the results obtained from experiments on animals, these factors must be able to be substantially improved. These experiments also made it possible to inventory the number of parameters on which these factors depend and the relative importance of some of them in the final result of statistical defibrillation efficiency. Implantable automatic defibrillators

  the best performers currently allow

  dre the energy threshold of a defibrillation discharge

  at a value of about 25 Joules under a voltage of

  between 1500 and 2500 volts with an efficiency rate

95%.

  The object of the present invention is to substantially improve these performances by increasing on the one hand the efficiency ratio for the energy threshold indicated above and on the other hand substantially decreasing the

  threshold of energy at a given efficiency rate.

  The present invention aims to provide the means necessary to obtain a result

  optimal defibrillation, taking into account the

  the environment and the various surgical implantation techniques, so as to obtain a defibrillation energy ratio

best possible.

  For this purpose, the invention relates to a high performance defibrillator, characterized in that

  it comprises at least one internal discharge electrode

  heart, located in the right ventricle and

  if external electrodes remote from the core in several different directions, external electrodes electrically connected to each other, the set of electrodes being connected to the corresponding circuit of a

  power and control box, external electrodes

  placed so that the current density across

  the ventricular myocardium is distributed evenly

  gene by a multitude of .lines of current passing preferentially through the thickest zones of the

  myocardium, representing the bulk of myocardial

  to obtain a defibrillation threshold and / or -5

minimal cardioversion.

  An additional feature is the retention in the right ventricle of the

  discharge in the separated position of each of the walls.

  A further feature of the invention is its particular ability to operate at high currents resulting from higher charge voltages without exhibiting any detectable harmfulness, due to the plurality, remoteness and range of electrodes which make it possible to achieve the multiple distribution of the effective lines of current through the myocardium reflecting the degree of homogeneity of the

  the distribution of the current through the heart.

  Another additional characteristic concerns the measurement of the current and a possibility of its adjustment in each of the electrical connections between the housing and the electrodes implanted externally to the core. A final additional feature is the evaluation of the performance of the electrode system and its optimal configuration on a

  subject given by application of the stimulation technique

  lation. The present invention will be well understood in the

  reading of the following description, made as a

  of non-limiting example on several embodiments and variants with reference to the accompanying drawings in which: Figure 1 is a general perspective front view in perspective and in section illustrating in transparency the basic principle of the invention without figuration of the links heaters; FIG. 2 is a double front view in transparency and in section along a plane transverse to the heart with figuration of the locations of the outer electrodes corresponding to the variant shown in FIG. 1; Figure 3 is an analogous view illustrating another alternative position of the electrodes;

  FIG. 4 is a frontal double view in trans-

  parence and section along a transverse plane passing through the endocavitary electrode with figuration of the locations of the outer electrodes corresponding to another variant; Figure 5 is a double view similar to that of Figure 4 showing another alternative position of the outer electrodes; Figure 6 is a view similar to that of the figure showing a further variant; FIG. 7 is the circuit diagram of the circuits of

  connection between the electrodes and the function blocks

  general terms of the circuits enclosed in the casing

power and control; -

  FIG. 8 is the electrical diagram of a variant

  with external casing to the body and external electrodes

in contact with the skin.

  The general inventive idea is to provide a defibriator Illateur comprising several electrodes of which

  the power and control box, electrodes im-

  plantable externally to the heart or in contact with the skin and arranged in different directions so as to allow a uniform distribution of the distributed current lines in weighted intensity according to general and elementary directions preferentially on the zones and walls of greater thickness or more large muscle mass in the ventricles

  for the efficiency of propagation and excitation

  individual cells and muscle fibers,

  these lines the current and directions-participant effective

defibrillation.

  One of the characteristics of the general inventive idea is therefore to create more efficient current lines in the regions of the

  ventricular myocardium of greater thickness.

  _; Thus, the present invention is totally

  independent of the type of defibrillator or defibrillator-

  lateur-cardioverteur used. It is equally applicable to conventional defibrillators as well as to simple or multifunctional defibrillators and in particular to discharge electrode defibrilators kept apart from the walls by appropriate means, in particular

  maintained centrally in the right ventricle.

  In the description that follows, the terms

  defibrillation and defibrillator include the cardioversion function and the device that implements it and the treatment concerns both ventricular fibrillation and ventricular tachycardia. Thus, the term fibrillation also covers the disorder of

ventricular tachycardia.

  The invention also applies to defibril-

  power box and external control box

  in the body as well as defibrillators'a box supply and control external to the body using several electrodes external to the body that is to say in contact with the skin and the watch

Figure 8.

  The defibrillator according to the invention applies to a heart 1 having a right atrium 2 and a right ventricle 3 and a left atrium 4 and a left ventricle 5 formed in a muscle called myocardium. The ventricles are separated by a wall 6 called septum. The myocardium is controlled so

  repetitive movements of contraction and relaxation-

  likely to present in some patients the

  risk of ventricular fibrillation access.

  This state of fibrillation can be reduced by an electric shock consecutive to the rapid and automatic discharge of a capacitor through the myocardium. The defibrillator according to the invention aims at

  triggering a unique and effective shock of

  low energy sparkle resulting from the discharge of a capacitor C. An electronic control, control and monitoring unit 7 is connected to a set S

  of electrodes inside the heart carried by a catheter

  ter 9 introduced into the heart by the superior vena cava. Said catheter carries at least one discharge electrode 10 located in the right ventricle 3, for example in the form of a ring, and, where appropriate,

  a distal electrode 11 and a third electrode

  of 12 located in the right atrium 2 at the mouth

of the vena cava.

  The inner electrodes are individually connected to the relevant circuits of the control and monitoring power supply box 7 which is

will describe below.

  The electronic box 7 of the defibrillator according to the invention is also connected to a set 13

  several electrodes external to the heart.

  These electrodes external to the heart are preferably implanted subcutaneously at the level of muscle or fat tissue around the thorax, but may also be external to the body in contact with the skin via a

electrically conductive gel.

  The electrical connection of the external electrodes

  in the heart can be done in different ways.

  Firstly, the electrodes are all individually connected to the corresponding circuit of the electronic unit 7. According to one variant, the electrodes are electrically connected to each other, one of them

  they only are connected to the case.

  Another variant consists in connecting the electrodes to one another via spark gaps such as 14 constituting as many short circuits for high discharge voltages but isolated at low voltage, gaps at the terminals from which it is possible to draw

an electrophysiological signal.

  -9- The outer electrodes at the heart -formant

  all 13 have the distinction of being

  core, that is to say, sufficiently far apart and extended in different directions to constitute a multidirectional preferential distribution of the effective lines of current, on either side of a direct line joining the discharge electrode and

  the outer electrode concerned.

  The effective lines of current thus form a solid angle whose summit is constituted by the discharge electrode and whose opening varies in

  function of the distance and the surface of the elec-

corresponding outer trode.

  Described below are the preferential zones

  location of the outer electrodes to the heart.

  Preferably, the electrodes are dis-

  placed in a transverse plane intersecting the thorax at the level of the ventricles and / or in a zone defined by

the left axillary line.

  According to a variant, the electronic unit 7 has a body 15 rendered electrically conductive and used as an electrode external to the core. In this case, it is preferably placed in the abdominal position

or subclavian.

  We will now describe hereinafter general positions in the areas defined above that can occupy the electrodes outside the heart this, in

reference to Figures 1 to 6.

  There are thus three-electrode configurations and two-electrode configurations only. They are divided into two groups: on the one hand axillary electrodes such as 16 or 17 or 16 and 17 in optimal number equal to two arranged preferentially in a: one or on the left axillary line and on the other hand 1S back electrodes or 19 or 18 and 19 located on the circumference of the thorax

outside the axillary area.

- 10 -

  Preferably, the back electrodes are located in the transverse plane intersecting the core at the placed discharge electrode 10

in the right ventricle.

  We will now examine, with reference to

  figures, some special cases of

  trodes outside the heart that led to results

remarkable states.

  One of the characteristic configurations concerns electrodes external to the heart contained in the transverse plane passing through the discharge electrode referenced 10, for one in the zone or on the left axiary line and for the other in the back.

  under one or other of the shoulder blades (Figure 3).

  A derived variant concerns the same type of general arrangement with two axillary electrodes in the zone or on the left axillary line disposed on either side of the transverse plane concerned (FIGS.

1 and 2).

  A simplified variant of the above has only two axillary electrodes located in the

  area or on the left axi lar line (Figure 4).

  Another variant presents a single electri-

  Axial trode I la lar in the transverse plane passing through the discharge electrode 10 and one or two dorsal electrode (s) located (s) in said transverse plane (Figure). One of the electrodes referenced 20, of smaller surface, is placed at the intersection of the plane

  concerned and of the zone or line I axi

  I.aire right. This is the particular case represented

on the figur-e 6.

  They also have the particularity of being disposed on either side of the core sharing axillary lateral external electrodes and dorsal electrodes and more particularly lateral dorsal electrodes so as to obtain a distribution

- 11 -

  preferential current lines of the discharge electrode through the septum and the left ventricle on the one hand and through the outer wall of the ventricle

right on the other hand.

  For surgical reasons, the number of implantable electrodes must be limited. A number

  greater than six is already considered excessive here.

  Thus, according to the preferred embodiments, the external electrodes are in a number between two and four, arranged laterally in the heart at the level of

  ventricles on both sides of the septum.

  It is understood that the fractionation of the intensity in several directions makes it possible, as indicated above, to increase or operate at higher discharge intensity levels without any fear of the harmfulness associated with the increase in the density.

of current flowing through the tissues.

  As indicated, there are two groups of electrodes, the first said lateral axillary and the so-called dorsal seconds and more particularly

  dorsal lateral located, for the latter, in a.

  transverse plane passing through the ventricles opposite

  of the myocardial wall of the right ventricle.

  The electrodes external to the core develop according to their position and their function on surfaces of the order of a few cm2 to a few tens of cm2 so as to open the solid angles of distribution of the effective lines of current from the discharge electrode and through the septum and the

  adjacent myocardium of the right or left ventricle.

  The electrode or dorsal electrodes (s) are or are arranged to develop effective lines of current laterally towards the back of the

  heart, through large masses of myocardium.

  With the observation of Figure 1, one can con-

  dramatically increase the multiplication and dispersion of the effective lines of current across a large area of the

- 12 -

myocardium of the left ventricle.

  In this region, the myocardium is thicker

  and it is necessary to multiply the effective current lines

  in each solid angle from the discharge electrode to each of the outer electrodes

lateral axi Illaires.

  The aim is to achieve, by playing on these parameters, totally a maximum mass of ventricular myocardium and more particularly, by higher intensities, the thickest regions of the myocardial muscle: left ventricle,

septum, apex.

  The distributions of the effective lines of current depend on the position and surface of the electrodes. We will be able to multiply more

  important the current lines crossing the ven-

  tricle left by an appropriate increase in the

  surface of the electrode or electrodes concerned.

  The effective lines of current to the right side of the heart seem to be less intense, presumably due to the lower thickness of the right ventricle. Also, can we be satisfied with a

  lower surface electrode on the right.

  According to various findings, the effects indicated above are obtained both with subcutaneous electrodes and with electrodes in contact with the skin and with a housing 7 located in

outside the body.

  The electronic box 7 encloses the various circuits for controlling, monitoring and controlling the charge and the discharge, as well as the battery or batteries P

  and the defibrillation capacitor C.

  As indicated, and according to one of the main advantages of the invention, the size of the capacitor is reduced because of the good energy efficiency of

  defibrillation related to this type of defibrillator.

  More precisely, but in a non

- 13 -

  In a limiting manner, the electronic box 7 contains a

  circuit 21 for detecting and monitoring batteries

  cardiac signals from an electro-

  physiological sample taken between the distal electrode and the discharge electrode for example, or between other electrodes. It also contains a circuit 22 for charging and discharging the capacitor C essentially formed by a high voltage converter powered from the battery P and controlled by a decision circuit comprising a locking loop automatically preventing a second charge after a first discharge by acting

  on the power switch of the charging circuit.

  As indicated, according to one of the preferred variants

  However, the means described above apply to discharge electrode type defibrillators held centrally in the right ventricle or having means for keeping it at bay.

walls.

  This maintenance provides a significant improvement in the efficiency of defibrillation for a given energy. The defibrillator according to the invention has a high efficiency rate. One discharge provides defibrillation. So, he. proceeds by a single, non-sequential shock as in other

less efficient defibrillators.

  To do this, as indicated above, the charging circuit includes a locking loop preventing any automatic recharging of the capacitor.

after a first discharge.

  The electrical connections of the external electrodes

  corresponding to the corresponding circuit of the housing 7 each having a peak current detector such as 23 used to optimize the confi uration of the electrodes

and their respective surfaces.

  The present invention also relates to

- 14 -

  a method of testing and evaluating the effectiveness of

  defibrillator comprising a plurality of external electrodes

  electrically connected to each other, in which the peak currents in the different connections connecting the external electrodes to the discharge circuit of the power supply and control box are measured at the moment of impact by means of the elements sensors and the like, inserted into the links and comparing these currents with each other so as to control and modify the electrodes or

  current intensities in each of the. electric links

  individual cells of the electrodes outside the housing. The invention also relates to a method

  test and evaluate the effectiveness of a defibril-

  having a plurality of external electrodes in which stimulation pulses are applied between the endocavity electrode used as the

  discharge and the external electrodes rel-

  trially between them and one verifies or modifies the positions of these electrodes or the intensities of the current supplied to these electrodes outside the heart until a higher stimulation threshold is obtained.

  possible or greater than a predetermined value.

  The invention has been described above in detail.

  It is understood, however, that various simple modifications, additions, direct variants, substitutions by equivalent means fall within the scope of the

present protection.

- 15 -

Claims (17)

  1. Defibrillator for patients suffering from severe disorders of the heart rhythm, characterized in that it comprises at least one discharge electrode (10) internal to the heart, located in the right ventricle and several outer electrodes (16 to 20) remote of the heart in several different directions, external electrodes electrically connected to each other   an assembly (13) electrically connected to the corresponding circuit   of an electronic control unit (7) supply and control, external electrodes placed so that the density of current through the ventricular myocardium is distributed. homogeneous manner by a multitude of current lines preferentially crossing the thickest areas of the myocardium representing the bulk of the myocardial mass in order to obtain a   defibrillation threshold and / or minimal cardioversion.   2. Defibrillator according to claim 1, characterized in that the defibrillation shock is unique and strong current is divided into several current directions.   - 3. Defibrillator according to claim 1,   characterized in that the number of implant electrodes   externally to the heart is between two and six.   4. Defibrillator according to the claims   -précédentes characterized in that each connection élec-   the individual electrodes outside the circuit   of the electronic control unit (7) for supply and control comprises detectors (23) making it possible to   measure the peak current flowing through this link.   Defibrillator according to claims 1,   2 and 3, characterized in that the implant electrodes   externally to the heart are placed subcutaneously at the level of the muscular tissues or   greasy on the periphery of the thorax. - 16 -   6. Deflibrillator according to claims 1,   2 and 3, characterized in that the outer electrodes are arranged in a transverse plane intersecting the   thorax at the height of the ventricles.   7. Defibrillator according to claim 6 characterized in that the transverse plane cuts the   thorax at the discharge electrode (10).   8. Defibrillator according to claim 6, characterized in that the outer electrodes (18) and (19) are arranged in the zone or on the left axillary line, the back electrode (s) being   arranged opposite the right ventricle.   9. Defibrillator according to claim 1,   characterized in that the electronic box (7) comprises   carries an implantable metallized body (15) placed in the abdominal or subclavian position used as   one of the electrodes outside the heart.   Defibrillator according to claim 8,   characterized in that it comprises two external electrodes   (18) and (19) placed in the zone or on the left axillary line, on either side of a transverse plane passing at the height of the electrode of   discharge (10) placed in the right ventricle.   11. Defibrillator according to the preceding claim characterized by an additional electrode is placed in the back.   Defibrillator according to claim 1,   characterized in that it comprises two external electrodes   (16) and (17) placed in the transverse plane passing at the height of: the electrode (10) located in the right ventricle, one being disposed at the intersection of this plane and the left axillary line and the other   in the back, under one or other of the shoulder blades.   Defibrillator according to the claims   previous ones, characterized in that the different electri-   outer trodes are of surface and of dimensions adapted to act on current lines effective in direction and intensity in order to obtain a minimum defibrillation threshold.   14. Defibrillator according to the claims   preceding, characterized in that the electrode of   charge (10) disposed in the right ventricle is provided with means for keep it away from the walls.   15. Defibrillator according to the claims of   1-4 characterized in that the outer electrodes   in the heart are external to the body.   16 Method for testing and evaluating a definition   brillator, characterized in that the peak currents in the different links connecting the outer electrodes to the circuits. of the power supply and control box are measured at the moment of impact by means of the sensors (24) and compared with each other so as to control and modify the surfaces and positions of the electrodes in order to obtain a threshold of minimal defibrillation.   17. Method for testing and evaluating a definition   brilliance, characterized in that im-   stimulation pulses between the endocavity electrode and the external electrodes electrically connected to each other and that the position of these external electrodes in the heart is verified or modified until   stimulation threshold as high as possible or higher than   to a predetermined value.